Method for purifying used oils



Jan 18, 1949. c. R. A. M. BJORNSTJERNA 2,459,409

METHOD FOR PURIFYING USED OILS Filed Feb. '4, 1946 Patented Jan. 18, 1949 METHOD FOR `PURIFYING USED OILS Curt Roger Adolf Ma gnus Bj'rnstjerna, Stockholm, Sweden, assignor to Aktiebolaget Separator, Stockholm, Sweden Sweden, a corporation of Application February 4, 1946, Serial No. 645,471

In Sweden Februaryl'l, 1945 Cl. ISS-16) 3 Claims.

Purification of different kinds of oils, particularly lubricating oils in systems providing continuous circulation of the oil, is a problem which is encountered in many machinery installations. In such plants it is customary to purify the oil of the impurities it has collected while circulating in the lubricating system. With small plants the whole quantity of circulating oil can be led through the purifying arrangement. This is generally impracticable with large plants. In such plants, in order that the purifying arrangement shall not be too cumbersome, means are provided to effect a so-called partial purification of the lubricating oil, the purifying system being arranged in parallel with the circulating lubricating system, whereby, by using a comparatively small purifying plant, the required degree of purity of the lubricating oil can be maintained.

It is desirable to keep the oil at a high temperature while it is being purified, thereby considerably facilitating the elimination of its impurities. However, certain difficulties are encountered when heating the oil; for example, its contained water and gases may be separated in the heating device as the oil passes slowly through it, or sludge from the oil may get burnt on to the interior of the heating device for the same reason.

Other difficulties, too, are encountered when thermostatically regulating the oils heating device, due to the great difference in temperatures between oil entering and oil leaving the heating device. i

By the present invention, having for its object a method of purifying oils containing sludge and/or water, and a practicable device to practice this method, an eiiicient purication of the oil, without the occurrence of the aforementioned drawbacks, is obtained by a construction and arrangement that may be described briefly as follows.

Between an oil tank and the purifier, the oil is passed through a circulating circuit equipped with a pump and a heating device. The circuit also contains an inlet for the oil coming from the oil tank and an outlet through which the heated oil, after all or part of the oil has circulated in the circuit for a suitable length of time, is led to the oil puriiier. The circulation circuit should then also comprise a deaerator in which the oil returning to the pump is freed of the gases, especially the air, contained in it.

The annexed drawing is a diagrammatic view of a plant embodying my invention and by means 2 of which my improved method may be practiced with maximum eiciency.

I is a storage tank for oil, e. g., the oil tank of an engine plant, from'which the oil is fed by a pipe 2 to the lubricating system of the engine, from which, by a pipe 3, the used oil is returned from the lubricating system. Both pipes should preferably enter the tank, as shown, at as great a distance from one another as practicable. From tank l extends another outow pipe 4, with a valve 5, a plug ii and a vacuummeter l, forming a so-called threshold 8. Oil is fed by pipe d to the oil purifying system arranged in parallel with the lubricating system. Pipe Il communi- Cates with the suction pipe 9 (the two pipes joining at a right angle) of a circulation circuit litted with a pump I0, a heating device ll and a deaerator I2.

The pump l0 is provided with an overilow valve I3, adjustable to any desired pressure and functioning here as a safety valve.

Pipe 9 is provided with a valve I4 also, with a tank I5. At the lowest point of the circulation circuit there is a plug I6 for drawing off the oil, and immediately before the heater II there is a plug Il for the same purpose.

From the deaerator I2 extends a pipe IIB fitted with a mano-meter I9, an adjustable valve 20 and a thermometer 2 l, and with, possibly, a nonreturn valve 22. The oil is fed through pipe I8 to a centrifugal separator 23 in which it is purified. In pipe I8 there is also a filling orice closed by a plug 24, through which the water. required to form the liquid seal in the separator, is admitted. The water may be led into the separator directly through pipe 25. The admission of water may take place during the separation, if there is a non-return valve 22, without the risk of water getting into the circulation circuit. The oil purified in the separator is discharged through a pipe 28, fitted with a pump 26 including an overflow valve '21, and also with a three-way cock 29, through which the puriiied oil may be led back via pipe 3l) to tank I, or be drawn off through an outlet 3| for testing and measuring the throughflow. rihe heavier `liquid separated in the separator is led away through the outlet 32. The heating device II should be preferably iitted with a manometer and safety valve.

The arrangement described has the following mode of operation: If there is no oil in the circulation circuit, plug 6 is screwed `ofi? and oil is then poured in up to the level determined by the threshold.` The air present in the circulation and possibly,

circuit may then escape through pipe I8 if valve 20 is kept open. After the oil has been poured in and plug 6 screwed in, pump IIl is started. Pump I should be a gear pump like pump 26, driven at a constant speed from separator 23.

Oil is then transferred from the suction side to the pressure side of the pump, a certain Vacuum being created on the suction side, the magnitude of which is determined partly by the resistance in the circulation circuit (chieily in the valve i4), partly by the re-leakage in the pump itself caused by the pump not being tight, and partly by the iiow resistan-ce in pipe d. The releakage will be smaller if the pump is kept moistened by oil, i. e., a higher vacuum can be maintained on the suction side of the pump when oil is being conveyed through it than when only air is passed through. In order that the air present on the suction side of the pump shall be expelled with certainty and oil be passed on to the circulation circuit from tank I by the sucking action of the pump, there should always be oil on the suction side of the pump. Instead of the oil being led away by the pump, fresh oil should be constantly ilowing up to it, a prerequisite for this being that, when the oil is being poured in, a suilcient quantity is introduced, which in turn necessitates that the cir culation circuit on the pumps suction side shall have the required volume. IThat part of the oil on the suction side of the pump which is transferred, when the pump is started, to the pressure side of the pump, must be sufficient to ll up the circulation circuit on the pressure side of the pump as far as the deaerator and tocreate also in the latter a liquid seal preventing the air entering the deaerator from passing back to the suction side of the pump through valve I4. Considering this, it may be necessary, in cas-e the volume of the suction pipe is not suicient, to

insert in pipe 9 a tank I5, indicated in the figure by dotted lines.

By arranging the circulation circuit in the Way described, the air in the feed pipe is eliminated relatively quickly from the circulation circuit via pipe I8 by pump It at the start, while oil from tank I is sucked into the circulation circuit through pipe 4.

It is obvious that th-e adjustment of valve I4 is of a certain importance, for if it is, for instance, kept quite closed, there will be no circulation in the circulation circuit. Then all the oil on the suction side of the pump in the circulation circuit may be transferred to its pressure side without there having been time meanwhile to remove the air present in pipe 4 and for oil from tank i to reach the pump. On the other hand, if valve i4 is kept somewhat open, a certain quantity of oil from the deaerator I2 is led back through the valve, whereby pump IU, if the aforementioned conditions regarding the volume of the suction pipe 9 are fuliilled, will be always kept moist and the propulsion of the air safeguarded.

By the aid of the vacuurnmeter one can regulate the adjustment of valve I4 during starting in such a Way that the greatest possible vacuum is continuously maintained in the feed pipe 4, and the highest possible efciency at the start of the circulation is obtained.

The threshold 8 serves mainly to prevent the oil returning from deaerator I2, during starting, from passing through feed pipe 4 to tank I, instead of getting into suction pipe 9. For this purpose, other devices may of course be used;

for instance, a guide plate, ejector or the like arranged at the connecting point between feed pipe 4 and pipe 9.

When the circulation in the circulation circuit has got started, valves i4 and 2t are so regulated that separator 23 works at the desired throughput. However, the separator must have been rst provided with the quantity of water necessary to form the liquid seal, the water being admitted through an opening that may be closed by plug 24.

The throughput can be determined by drawing off th-e oil from the separator through pipe 3l. By simultaneously reading the manometer I9, the valve I4 may, at a certain adjustment of valve 2D, be so calibrated that, subsequently, the desired throughput may be obtained by simply adjusting the valve Id, while reading the pressure on manometer It. It is evidently also possible to graduate manometer E9 so that it gives a direct indication of the throughilow.

Despite the fact that only a small part of the oil quantity flowing through the heater II is normally led to the separator, a high speed ci flow can be maintained in the heater, which causes a good heat transmission to be obtained, and, at the same time, prevents the separation of water and gases in the heating device and the burning onto it of sludge deposits.

With the circulation circuit arranged in the way described, there is the additional advantage that a very accurate regulation of the oil quantity fed to the separator may be effected in a simple way by the two valves I4 and 20 or, after adjustment of valve 2t, even by valve I4 alone. The oil quantity fed to the separator will be, besides, more independent of the pressure variations in the deaerator caused, for instance, by changes of the liquid level in tank I; this desirable condition being insured by the overpressure which may be kept in the circulation circuit by the throttling caused by valve 2Q.

Further advantages are attained at thermostatic regulation of the heating devices and are largely rendered possible by the described utilization of the circulation circuit. The thermostat, which, for obvious reasons, should be located at the outlet side oi th-e heater, will thus be more rapidly affected, due to the high velocity of the oil at breaking interruption of the current, by oil heated in the heater to the limit temperature. On the other hand, the temperature variations caused by the inertia oi the thermostat will be reduced, and th-e interval between engaging and disengaging the heater prolonged, due to the difference, reduced by the circulation, between the oil temperatures at the inlet side and outlet sides of the heater.

It is important that the two liquid currents in pipes 4 and 9 shall not disturb each other. This is avoided by joining pipe 4 with pipe 9 at a substantial angle, preferably a right angle. If pipes 4 and 9 were, for example, arranged in parallelism, the oil, flowing from the deaerator at a relatively high speed, might then flow on directly through pipe 4, through which the oil of the circulation circuit would be rapidly returned to tank l. It is also important that the pump l be placed so that the maximum possible oil quantity letl into suction pipe e can flow to the pump, so that it is really kept moistened with oil during the starting period.

Valve Ei, located in pipe 4, is intended for use mainly when the purifying system is common to two or more plants.

If the system is quite open, i. e. without a nonreturn Valve, and if the purifying plant is shut by stoppage of the pump ID, at least part of the oil in the circulation circuit will flow back to tank l. If then valves I4 and 20 are open, the part of the circulation circuit lying above the ljunction of feed pipe 4 and pipe 9 will be completely emptied by back ilow of the oil to tank l. The quantity of oil remaining in the circulation circuit is then such as to render possible, at the start of the pump, the rse-establishment of the circulation in the circulation circuit in the way described above, without the necessity of adding fresh oil through the opening closed by plug 6. It is evident that in this case the location of the heating device ll at a lower level than the junction of pipes 4 and pipe 9, as shown on the drawing, is of importance, as when the pump is stopped, it will remain full of oil, Whereby the volume of the suction pipe can be reduced correspondingly, if, when the oil is poured in, care be taken that the oil level is approximately as high on the pressure side as on the suction side in the circulation circuit, which, because the oil leakage in the pump should be as small as possible, can be brought about by keeping the pump running also during the oil filling. Should valve H be shut, for some reason, when pump l 0 comes to a standstill, the entire circulation circuit, ex cepting the deaerator, may be emptied by the suction action of the oil column in inlet pipe 4. In order that, also in this case, the circulation will be re-established, when the pump is started, Without the necessity of introducing fresh oil into the circulation circuit, it is necessary to retain in the deaerator sufficient oil both to fill up the part of the circulation circuit situated on the pressure side of the pump as far as the deaerator and also to form the liquid seal in the deaerator, preventing the air from passing from the deaerator to the suction side of the pump.

The herein described arrangement may be modified in various details Without departing from the invention. For example, one or both of the valves I4 and 20 may be replaced by fixed throttling discs with their through-flow area fixed beforehand. Valve I4 may be a spring-loaded valve adjustable for a certain pressure. Valve I4 may be also arranged in such a way that it can never be quite closed. These modications are merely illustrative of permissive variations from the specific disclosure.

What I claim and desire to protect by Letters Patent is:

l. A method for the continuous puriiication of used oil, which comprises pumping oil through an endless circuit and heating the oil in a heating locus during its passage through the circuit, continuously flowing oil to be puried from a source of Supply into said circuit at la rate less than the rate of flow through the heating locus, continuously releasing a part of the oil owing through said circuit while reconveying through said circuit the part of the oil not so released, and purifying the released oil and returning it to the supply.

2. The method defined in claim 1 in which gas flowing with the heated oil is removed and released along With the part of the oil that is released from the circuit for purication.

3. The method defined in claim 1 in which only a minor portion of the quantity of oil heated per unit of time in the circuit is released for purification, thereby maintaining a high rate of flow through the heating locus and substantially preventing separation of Water during heating and the burning of sludge deposits at said locus while at the same time insuring good heat transmission.

CURT ROGER ADOLF MAGNUS BJORNSTJERNA.

REFERENCES CITED The following references are of record in the iile of this patent:

UNITED STATES PATENTS Number Name Date 1,359,453 Watson Nov. 16, 1920 1,694,478 Miller Dec. 11, 1928 1,824,498 Rodman et al. Sept. 22', 1931 1,836,338 Rodman et al. Dec. 15, 1931 2,061,666 Miller Nov. 24, 1936 2,081,632 McBain May 26, 1937 2,223,999 Miller Dec. 3 1940 2,286,369 Miller June 16, 1942 2,320,106 South May 251, 1943 FOREIGN PATENTS Number Country Date 567,420 France Dec. 6, 1923 

